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1.
A. Salmoun R. Brédy J. Bernard L. Chen S. Martin 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2008,47(1):55-61
Electron capture processes in collision between slow
X7+ (X = N, O and Ne) ions and C60 fullerene have been
investigated using coincident measurements of the number n of ejected
electrons, the mass and charge of the multicharged C60
r+ recoil ions and their fragments Cm
i+ and the final charge state of the
outgoing projectiles X(q-s)+ (
). The
collision velocity is about 0.4 a.u. The partial cross-sections σr
s , corresponding to r electrons transferred to the projectile with only s electrons stabilized, have been measured. Cross-sections
for collisions “inside” and those “outside” the C60
cage have been separated by analyzing the kinetic energy of the outgoing
projectile. The mean final charge state for frontal collisions has been
measured to 3.1, 2.6 and 2.5 for N7+, O7+ and Ne7+
respectively. These results show the importance of the core effect on the
stabilisation processes of captured electrons. 相似文献
2.
T. Majima K. Tono A. Terasaki Y. Kawazoe T. Kondow 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2007,43(1-3):23-26
The electronic and geometric structures and photodissociation dynamics of the chromium trimer ion, Cr3
+, were investigated by photodissociation spectroscopy in the photon-energy range from 1.32 to 5.52 eV.
The branching fractions of the product ions, Cr+ and Cr2
+, exhibit stepwise changes at the threshold energies for dissociation into Cr++Cr2, Cr+Cr2
+, Cr++2Cr, and Cr*+Cr2
+.
It is noted that Cr2
+ is produced even above the threshold for atomization; the excess energy is redistributed to produce a fragment atom, Cr*, in an excited state.
The photodissociation action spectrum is well explained by a mixture of simulated spectra for two nearly-degenerate structural
isomers identified by density functional calculations:
those having a metastable C2v structure and the most stable structure slightly distorted from the C2v one.
The barrier height between the two isomers which is lower than the zero-point energy suggests that Cr3
+ has an intrinsically floppy structure. 相似文献
3.
4.
N. Hori A. Furuya M. Tsuruta F. Misaizu K. Ohno 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2007,43(1-3):41-44
Photoinduced dissociation in the ultraviolet region has been investigated for Ag nF n-1
+ cluster ions. Photodissociation spectrum of
Ag2F+
in the energy of 3.8–5.6 eV exhibits several sharp bands corresponding to the transition to electronically excited states.
In this dissociation, only the Ag2
+ ion was observed as a fragment ion. Theoretical calculation indicates that the parent Ag2F+ ion has a linear Ag-F-Ag equilibrium geometries in the ground and excited states. Since conformational changes by excitation
of bending vibration are necessary for the fragmentation of an F atom, this indicates that production of Ag2
+ from Ag2F+ is a result of internal conversion and following conformational changes. 相似文献
5.
Metastable fragmentation of silver bromide clusters 总被引:2,自引:0,他引:2
J.-M. L'Hermite F. Rabilloud L. Marcou P. Labastie 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2001,14(3):323-330
The abundance spectra and the fragmentation channels of silver bromide clusters have been measured and analyzed. The most
abundant species are AgnBrn - 1
+ and AgnBrn + 1
- and Ag14Br13
+ is a magic number, revealing their ionic nature. However, some features depart from what is generally observed for alkali-halide
ionic clusters. From a certain size, AgnBrn - 1
+ is no more the main series, and AgnBr n - 2, 3
+ series become almost as important. The fast fragmentation induced by a UV laser makes the cations lose more bromine than
silver ions and lead to more silver-rich clusters. Negative ions mass spectra contain also species with more silver atoms
than required by stoichiometry. We have investigated the metastable fragmentation of the cations using a new experimental
method. The large majority of the cations release mainly a neutral Ag3Br3 cluster. These decay channels are in full agreement with our recent ab initio DFT calculations, which show that Ag+-Ag+ repulsion is reduced due to a globally attractive interaction of their d orbitals. This effect leads to a particularly stable trimer (AgBr)3 and to quasi-planar cyclic structures of (AgBr)n clusters up to n = 6. We have shown that these two features may be extended to other silver halides, to silver hydroxides (AgOH)n, and to cuprous halide compounds.
Received 9 November 2000 and Received in final form 25 January 2001 相似文献
6.
M. Vogel K. Hansen A. Herlert L. Schweikhard 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2002,21(2):163-166
The dimer dissociation energies of gold cluster ions Au
+
n
, n
= 9, 11, 13, 15 have been determined with an extension of a recently developed model-independent method. Monomer-dimer decay
pathway branching ratios provide the energy dependent process which is needed in this method. The measured values are D
2
(
Au
+
9
) = 3.66(8)(9) eV, D
2
(
Au
+
11
) = 4.27(11)(8) eV, D
2
(
Au
+
13
) = 4.50(9)(7) eV and D
2
(
Au
+
15
) = 4.29(10)(6) eV.
Received 13 May 2002 / Received in final form 22 July 2002 Published online 24 September 2002
RID="a"
ID="a"e-mail: manuel.vogel@uni-mainz.de 相似文献
7.
M. Bertolus V. Brenner P. Millié 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2000,11(3):387-394
An ab initio study of the Nan(OH)n, Nan(OH)n-1
+, Agn(OH)n, and Agn(OH)n-1
+ clusters with n up to four is presented. The results of this study show that, in accordance with experimental observations, the sodium hydroxide
clusters are almost purely ionic, while the Ag-O bond exhibits a significant covalent character. The perturbation caused by
the non-spherical OH- group relatively to an atomic anion, as well as the influence on structures and energies of the covalent character of the
metal-oxygen bond are determined. The appearance of metal-metal bonds in the silver hydroxide clusters is also discussed.
Finally, the theoretical results obtained on the Na-OH clusters are compared to experimental results available on the dissociation
of the Nan(OH)n-1
+ clusters.
Received 9 August 1999 and Received in final form 1st December 1999 相似文献
8.
H. Nagao K. Awazu S. Hayakawa K. Iwamoto M. Toyoda T. Ichihara 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2007,45(2):279-287
Various dissociation channels of silver bromide cluster ion
Ag2Br+ and silver cluster ion Ag3
+ were observed in
high-energy collisionally-activated dissociation (CAD) using a Cs target.
The fragment patterns of the high-energy CAD were compared with those of the
metastable dissociation and low-energy CAD. The difference in the fragment
patterns between the high-energy CAD and the other dissociation methods was
explained in terms of the internal energy distributions. The dissociation
mechanisms of neutral silver bromide cluster Ag2Br and silver cluster
Ag3 were also investigated by charge inversion mass spectrometry using
the Cs target. While the fragment ions AgBr- and Ag2
- were
dominantly observed in the charge inversion spectrum of Ag2Br+,
the undissociated ion Ag3
- was observed as a predominant peak in
the case of Ag3
+. The dissociation behavior of Ag2Br*
can be explained on the basis of the calculated thermochemical data.
Contrary to this, the predominant existence of the undissociated
Ag3
- cannot be explained by the reported thermochemical data. The
existence of undissociated Ag3
- suggests that the dissociation
barrier is higher than the internal energy of Ag3
*
(theoretical: 1.03 eV, experimental: 2.31 eV) estimated from the ionization
potentials of Ag3 and Cs. 相似文献
9.
M. Vogel K. Hansen A. Herlert L. Schweikhard 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2001,16(1):73-76
The decay pathway competition between monomer and dimer evaporation of photoexcited cluster ions Au
+
n, n = 2-27, has been investigated by photodissociation of size-selected gold clusters stored in a Penning trap. For n > 6 the two decay pathways are distinguished by their experimental signature in time-resolved measurements of the dissociation.
For the smaller clusters, simple fragment spectra were used. As in the case of the other copper-group elements, even-numbered
gold cluster ions decay exclusively by monomer evaporation, irrespective of their size. For small odd-size gold clusters,
dimer evaporation is a competitive alternative, and the smaller the odd-sized clusters, the more likely they decay by dimer
evaporation. In this respect, Au
+
9 shows an anomalous behavior, as it is less likely to evaporate dimers than its two odd-numbered neighbors, Au
+
7 and Au
+
11. This nonamer anomaly is typical for copper-group cluster ions M
+
9 (M = Cu, Ag, Au) and a similar behavior is found in the anionic heptamers M
-
7. It is discussed in terms of the well-known electronic shell closing at n
e = 8 atomic valence electrons.
Received 2 November 2000 相似文献
10.
R. von Pietrowski K. von Haeften T. Laarmann T. Möller L. Museur A. V. Kanaev 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2006,38(2):323-336
The electronic and geometric structure of rare gas clusters doped with
rare-gas atoms Rg = Xe, Kr or Ar is investigated with fluorescence excitation
spectroscopy in the VUV spectral range. Several absorption bands are
observed in the region of the first electronic excitations of the impurity
atoms, which are related to the lowest spin-orbit split atomic 3P1
and 1P1 states. Due to influence of surrounding atoms of the
cluster, the atomic lines are shifted to the blue and broadened
(“electronical cage effect”). From the known interaction potentials and
the measured spectral shifts the coordination of the impurity atom in
ArN, KrN, NeN and HeN could be studied in great detail.
In the interior of KrN and ArN the Xe atoms are located in
substitutional sites with 12 nearest neighbours and internuclear distances
comparable to that of the host matrix. In NeN and HeN the cluster
atoms (18 and 22, respectively) arrange themselves around the Xe impurity
with a bondlength comparable to that of the heteronuclear dimer. The results
confirm that He clusters are liquid while Ne clusters are solid for N≥
300. Smaller Ne clusters exhibit a liquid like behaviour. When doping is
strong, small Rgm-clusters (Rg = Xe, Kr, Ar, m≤10 2) are formed
in the interior sites of the host cluster made of Ne or He. Specific
electronically excited states, assigned to interface excitons are observed.
Their absorption bands appear and shift towards lower energy when the
cluster size m increases, according to the Frenkel exciton model. The
characteristic bulk excitons appear in the spectra, only when the cluster
radius exceeds the penetration depth of the interface exciton, which can be
considerably larger than that in free Rgm clusters. This effect is
sensitive to electron affinities of the guest and the host cluster. 相似文献
11.
C. Bréchignac Ph. Cahuzac B. Concina J. Leygnier 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2001,16(1):91-94
We have studied experimentally the collisional charge transfer between a neutral atom and a multicharged metal-atom cluster.
The charge transfer cross section measured for Na 31
+ + + Cs is in the range of 400 ?2. The time-of-flight mass analysis of the singly charged collision products demonstrates that an energy of about 0.5 eV is
deposited in the cluster fragment during the charge transfer collision. This effect can be interpreted as a charge transfer
to an excited state of the metal cluster. The measured cross section for Na 31
+ + + Cs is larger than the one for Na 31
+ + Cs collisions. This difference between these two systems is due to the existence, for the first one, of a Coulombic repulsion
term in the collision output channel.
Received 24 October 2000 相似文献
12.
A. Qayyum M.N. Akhtar 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2000,12(1):181-184
Light emission during sputtering of graphite targets with 1–10 keV Ne+, Kr+ and Xe+ beams has been investigated in the 180-600 nm wavelength range. Beside the characteristic lines of sputtered C1 and C1
+, a continuum superimposed with a number of broad structures was observed in the 250-520 nm range, and having a maximum at
386 nm. Mass analysis of the sputtered flux confirmed the presence of negative carbon clusters C
m
-
, C2
- being the dominant one. Ion beam parameters i.e. ion mass, energy, current density and ion dose were varied to identify the origin of the continuum emission. On the basis
of the experimental results, it is suggested that the continuum is predominantly due to the overlapping of various band systems
of sputtered C2 with a small contribution from the heavier sputtered carbon clusters Cm (m>2).
Received 24 September 1999 and Received in final form 11 February 2000 相似文献
13.
K. Guch J. Fedor S. Matt-Leubner R. Parajuli C. Mair A. Stamatovic O. Echt C. Lifshitz J. Harvey F. Hagelberg Z. Herman M. Probst P. Scheier T. D. Märk 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2003,24(1-3):131-136
The recent addition of (i) a third sector field to our two
sector field mass spectrometer (resulting in a BE1E2 field
configuration) and of (ii) a high performance electron gun
enables us now to study in detail the time dependence of the
kinetic energy release distribution (KERD) over a relatively
wide range of cluster ion lifetimes. Using this newly
constructed device we have studied here for the first time KERDs
and deduced binding energies BEs (using finite heat bath theory)
of large rare gas cluster ions (an upper size limit in earlier
studies arose from the fact that different naturally occurring
isotopes will contribute to a chosen metastable peak when the
size exceeds a certain value) and in addition of fullerene ions
smaller and larger than
(here again contaminating
coincidences did not allow such studies earlier). Moreover, high
precision KERD measurements for the decay of rare gas dimer ions
in conjunction with model calculations (using recently
calculated potential energy curves for the rare gas dimer ions)
also enable us to obtain information on the dynamics and the
mechanisms of the underlying spontaneous decay reactions
. In addition, we are also reporting
here a novel method (unified breakdown graph method) to
determine cluster ion binding energies using a recently
constructed tandem mass spectrometer BESTOF allowing us to
measure fragmentation patterns arising from the unimolecular
decay of molecular cluster ions induced by surface collisions.
The fragmentation and reaction patterns of protonated ethanol
cluster ions investigated here clearly demonstrate in contrast
to some of the earlier cluster ion studies that unimolecular
dissociation kinetics determines the formation of product ions
in the surface-induced decomposition. 相似文献
14.
T. Iino K. Ohashi K. Inoue K. Judai N. Nishi H. Sekiya 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2007,43(1-3):37-40
Vibrational spectra of mass-selected
Ag+(H2O)n ions are measured by infrared photodissociation
spectroscopy and analyzed with the aid of density functional theory
calculations. Hydrogen bonding between H2O molecules is found to be
absent for cold Ag+(H2O)3, but detected for
Ag+(H2O)4 through characteristic changes in the position and
intensity of OH-stretching transitions. The third H2O coordinates
directly to Ag+, but the fourth H2O prefers solvation through
hydrogen bonding. The preference of the tri-coordinated form is attributed
to the inefficient 5s–4d hybridization in Ag+, in contrast to the
efficient 4s–3d hybridization in Cu+. For Ag+(H2O)4,
however, di-coordinated isomers are identified in addition to the
tri-coordinated one. 相似文献
15.
F. Calvo F. Spiegelman M. A. Gaveau M. Briant P. R. Fournier J. M. Mestdagh J. P. Visticot 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2003,24(1-3):215-218
The finite temperature optical spectroscopy of
CaArn clusters in the range
6
n
146
is investigated using a Diatomics-In-Molecule (DIM) Hamiltonian
and classical parallel tempering Monte Carlo simulations. The
absorption spectrum is calculated in the vertical approximation
at various temperatures between 2 K and 50 K. Several typical
situations are reported. CaAr6 shows a
strong thermal broadening and shift of the spectral lines,
possibly associated with isomerization.
CaAr13 only shows some broadening.
CaAr37 exhibits features corresponding to
coexisting isomers at low temperature. Finally, the abrupt
changes in the absorption spectrum in
CaAr146 at about 20 K are indicative of
surface diffusion. 相似文献
16.
Solcà N. Dopfer O. 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2002,20(3):469-480
Infrared (IR) photodissociation spectra of the aniline+-Arn cations, An
+
-
Ar
n
(n
= 1, 2), are analyzed in the vicinity of the N-H stretch fundamentals. The complexes are produced in an electron impact (EI) ion
source which produces predominantly the most stable cluster isomers. Two isomers of An+-Ar are identified by their characteristic N-H stretch frequencies: the planar proton-bound global minimum, in which the Ar
ligand forms a nearly linear H-bond to the amino group, and the less stable π-bound local minimum, in which the Ar atom is attached to the π-electron system of the aromatic ring. This result is the first unambiguous detection of the most stable H-bound An+-Ar dimer. All previous spectroscopic studies of An+-Ar employed resonance enhanced multiphoton ionization (REMPI) of neutral An-Ar and identified only the less stable π-bound cation due to restrictions arising from the Franck-Condon principle. The EI-IR spectrum of An+-Ar2 shows that the most stable structure of this trimer features two equivalent H-bonds (C2v symmetry). The interpretation of the experimental data is supported by quantum chemical calculations. The ab initio potential of An+-Ar calculated at the UMP2/6-311G(2df, 2pd) level features H-bound global minima ( D
e
= 513 cm-1) and π-bound local minima ( D
e
= 454 cm-1), with a barrier of V
b
≈ 140 cm-1 for isomerization from the π-bound toward the H-bound minimum.
Received 4 February 2002 Published online 13 September 2002 相似文献
17.
S. Nonose S. Iwaoka H. Tanaka N. Okai T. Shibakusa K. Fuke 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2003,24(1-3):335-338
Photo-induced reaction of
[Fe(III)-protoporphyrin]+
(hemin+) ions solvated with
dimethylsulfoxide (DMSO) is investigated by using a tandem mass
spectrometer with electrospray ionization. We measure the
photodissociation yields of mass-selected
hemin+(DMSO)n
clusters for n = 0-3. The
mass spectra of the fragment ions show the -cleavage of
carboxymethyl groups in addition to the evaporation of solvent
molecules. Yield of the -cleavage reaction is found to depend
strongly on the excitation energy and the number of solvent
molecules. We also examine photo-induced reactions of
multiply-charged cytochrome c ions, (M + nH)n + (
n = 9-17). Photoionization is
found to be the dominant process for the lower charged states (
n = 9-12) and its yield
decreases rapidly with increasing the charge. The
photoionization is ascribed to the emission of electron by
multiphoton excitation of heme under the influence of Coulomb
attractive potential arising from the charges in the polypeptide
chain. Model calculations of the Coulomb potential suggest that
the structure of the polypeptide chain is completely elongated. 相似文献
18.
C.-K. Siu S. J. Reitmeier I. Balteanu V. E. Bondybey M. K. Beyer 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2007,43(1-3):189-192
Pt4
- catalyses the conversion of CO and
N2O to CO2 and N2 in the gas phase, as observed by Fourier
transform ion cyclotron (FT-ICR) mass spectrometry. The partial pressures of
CO and N2O determine the extent of poisoning and the turnover numbers
that can be achieved. The catalytic conversion terminates as soon as two CO
are adsorbed on the cluster. With N2O, the reactivity of
Pt4O2
- and Pt4O3
- is reduced to 41% and
34% compared to Pt4O-, respectively, and with
Pt4O4
- this value is reduced to 1%. In contrast,
Pt4
+ shows no apparent catalytic activity. Density functional
theory calculations of Pt4
+/- with CO and N2O adsorbates
reveal significantly different stabilities of the reaction intermediates for
the different charge states. 相似文献
19.
Non-relativistic configuration interaction (CI) ab initio calculations using large basis sets have been carried out to determine the potential curves of the first electronic states of Ne2 +, Ar2 + and Kr2 +. The spin—orbit interaction was treated assuming that the spin—orbit coupling constant is independent of the internuclear separation (R). For Ar2 +, calculated dissociation energies and equilibrium separations are in good agreement with experimental results. The calculations for Ne2 + suggest that the lowest vibrational level of the I(1/2u) ground state observed by threshold photoelectron spectroscopy by Hall et al. [1995, J. Phys. B: At. molec. opt. Phys., 28, 2435] and assigned to either ν = 0 or ν = 2 actually corresponds to ν = 4. The calculations also predict the I(1/2g) state of Ne2 + and Ar2 + to possess a double-well potential and that of Kr2 + to be repulsive at short range and to only possess a single shallow well at large internuclear separation. The ab initio calculations provide an explanation for the observation made by Yoshii et al. [2002, J. chem. Phys., 117, 1517] that Kr2 + and Xe2 + dissociate after photoemission from the II(1/2u) state to the I(1/2g) state whereas Ar2 + does not. 相似文献
20.
P. Feiden J. Leygnier Ph. Cahuzac C. Bréchignac 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2007,43(1-3):49-52
Condensation of nano-droplets in a supersaturating vapor decomposes in two steps: the formation of a nucleation center, also
called critical nuclei or nucleation seed, and the growth sequence, by accretion of further atoms on the nucleation center.
These two steps have been investigated separately through the clustering of homogeneous particles Nan and heterogeneous particles NanX in a helium buffer gas (X = (Na2O)2 or (NaOH)2). The growth sequence is analyzed with preformed molecules X injected in a supersaturating sodium vapor and driving production
of NanX clusters.
Cluster distribution mean sizes are controlled by sodium concentration and by the condensation cell effective length. The
signal intensities observed for homogeneous and heterogeneous clusters are proportional to the homogeneous and heterogeneous
nucleation center numbers respectively. We can measure the efficiency for the homogeneous nucleation center production versus
sodium concentration. This process is the onset of the condensation phase transition. 相似文献